In environments where overhead roll-up doors are used, there are two transverse forces which must be accounted for to insure proper and safe function of the door as the door panel travels vertically in the side columns bounding the path of travel for the door panel.
The first of these transverse forces that must be accounted for is a wind force or a wind load applied to the door panel, particularly as the door opens and closes. This transverse force typically results from a wind blowing against the door panel, and is particularly concerning when the door panel is opening or closing as the door panel may be blown out of its path of travel. If the door panel does not contain enough wind resistance to overcome the wind load applied to it, the door panel will disengage from the side columns, leading to the door unexpectedly opening or not properly opening or closing, and potentially damaging the door and any objects or persons located proximate the door panel. In order to combat this force and to increase the wind load, the door and door panel can withstand, the opposing side edges of the door panel may include a continuous thickened edge which engages the corresponding side column to prevent the door panel from blowing out when the door panel is confronted with a low, moderate, or even high wind load. However, if located in a high-wind area, these thickened edges may become severely worn and damaged over time—as constant and/or substantial wind blowing against the door panel may cause the thickened edges to continuously engage the side columns, substantially increasing the frictional forces between the side column and the thickened edges, particularly as the door panel opens and closes. As a result, the thickened edges may engage the side columns as the door panel is moved vertically between the opened and closed position, inhibiting door panel movement and substantially increasing wear.
The second of these transverse forces which must be accounted for is the force created when an object, like for example a forklift truck or a flat back truck, hits or impacts the door panel, usually as the door panel is opening or closing. In order to avoid damage to the object striking the door panel, the door panel, and any other door structures, like for example a bottom bar attached proximate the bottom edge of the door panel, the side columns, or a motor driving the door panel, it is desired that these doors be designed to “breakaway” so that the door panel is released from the side columns and pushed out from the resulting impact force. This breakaway ability, however, may be lessened or severely limited due to the friction between the thickened side edges and side columns when the door is impacted. Just as when a wind force or wind load is applied to the door, the application of an impact force from an object may cause the thickened edges to engage, or further engage, the side columns, creating a frictional force which acts to keep the door panel in place. While angling the innermost faces of the thickened edges that engage the side columns and/or a portion of the side columns that engage the thickened edges may facilitate the disengagement of the door panel from the side columns, there nevertheless is increased friction that may prevent the door panel from fully disengaging.
An additional problem related to the second transverse force and continuous thickened edges is that the edges may stick or jam in the side columns when the door panel is impacted, preventing the door panel from releasing from the side columns. If the continuous thickened edges become jammed in the side columns, because for example they are too thick or friction prevents their complete escape, the ability of the door to disengage from the side columns may be greatly compromised. If these thickened side edges become stuck or jammed in the side column when the door panel is struck, the sticking or jamming may damage the door panel, the thickened edges, or the side column, and may further prevent the motor from raising the door panel, potentially damaging the motor and preventing any self-repair features of the door panel from working. Once damaged, in order to repair the doors and get the door panel moving again, frequently a portion of the side column must be removed so the continuous thickened edge can be un jammed and placed back in the path of travel in the side column, and any door components which were damaged must be removed and replaced before full operation may be resumed.
In order to prevent unwanted wear from friction on these continuous thickened edges, and to further enhance the disengage-ability of the door panel when it is impacted by an object, it is known in the art to bond an ultra high molecular weight (“UHMW”) plastic strip, or more likely strips, to an angled face of the thickened edge which engages the side columns. While these plastic strips may reduce friction between the thickened edges and the side columns—thereby reducing the wear on the thickened edges and facilitating the disengagement of the edges and side columns when necessary—UHMW plastic strips have numerous drawbacks. First, bonding the plastic strip(s) to the door panel is highly labor intensive inasmuch as the strips must be broken apart sufficiently small and properly spaced to insure the door panel will properly wind up on the drum in a manner where the strip(s) do not enlarge the rolled door an overly inconvenient amount. A larger roll size when the door is in the substantially opened position results in a larger header for the door to house the rolled panel, thereby creating a smaller doorway or opening through which objects may travel. Second, because they are bonded and are a non-continuous piece, these plastic strip(s) contain edges or corners which are commonly caught and can tear or be peeled off entirely, creating an area which may be less disengage-able, leading to damage to the door panel, the side column, or any other door components if the door panel is impacted and cannot fully release. In order to replace any damaged or removed strips, the door panel must be disengaged from the side column, and a person must replace each strip individually by hand.
A third drawback to using UHMW plastic strips related to the tearing and peeling of the strip(s) is that adhesive must be used which may lead to an increase in the frictional forces recognized by the door, or worse hold the door panel in place if any of the strip(s) become torn or removed from the thickened edge. Adhesive remaining on the thickened edge after a plastic strip(s) is torn or removed may increase the friction between the thickened edge portion where the strip(s) has been removed or even form a bond between the thickened edge and side column locking the thickened edge and door panel in place. Additionally, before operation of a repaired door panel may begin, it may be necessary to properly clean at least a portion of the side column, to insure that no adhesive remains to prevent additional friction or sticking.
Another known method of preventing unwanted wear friction on these continuous thickened edges, and to further enhance the disengage-ability of the door panel when it is impacted by an object, is applying Polyethylene Terephthalate (“PET”) fabric strips over an angled face of the thickened edge, wherein the angled face comprises the portion which engages the side column. While applying the PET fabric strips are less labor intensive than bonding separate UHMW plastic strips, it still requires an individual to bond the fabric strips to the thickened edges. In addition, like the UHMW plastic stripes, PET fabric strips also contain edges making the fabric strips susceptible to being torn or partially removed from the edge. Additionally, these fabric strips may become worn or cut over time, creating additional edges that may catch or tear on the fabric. These fabric strips may also buckle and separate from the thickened edge, creating further hazardous conditions. Like the UHMW plastic strips, repairing any torn or removed portions of the fabric strips requires removing the door panel from the side columns, and in many cases may require the removal and replacement of the entire damaged fabric strip.
It is also known in the art, that in order to maintain breakaway-ability, the thickened edges may be made of a pliable material or may be made to protrude perpendicularly from the door panel a small distance. However, utilizing either of these methods to maintain breakaway-ability reduces the wind load the door panel can withstand before being blown out of the side columns inasmuch as the thickened edges are either too weak or too small to withstand a full wind load. Conversely, if a rigid material is utilized for the thickened edges or the thickened edges protrude a great distance from the door panel, the thickened edges may not properly disengage, or may not disengage at all when the door panel is impacted. While altering the material and thickness of the thickened edges may improve the response to one of the two transverse forces, it will have a negative impact on the other force. Additionally, there is still the issue of friction and additional issues of concern with roll-up doors employing thickened edge wind locks.
Regardless of the application of UHMW plastic strips, PET fabric strips, or applying nothing at all to the thickened edges, and regardless of whether the thickened edges contain an angled face, utilization of a continuous thickened edge along each side of the door panel substantially increases the diameter of the door panel when it is substantially wound on the drum in a substantially open position. The larger diameter requires a larger header that consequently may result in a smaller opening and may lead to additional unwanted wear on the motor controlling the drum and the door. Additionally, the thickened edges may crease, buckle or otherwise bulge when the door panel is in the rolled-up position, potentially damaging the edges and substantially increasing the size of the rolled-up door panel.
Additionally, continuous thickened edges may increase the total weight of the door, creating additional stress on the motor controlling the door as it opens and closes.
In yet other door designs, in order to enhance the wind lock of the door panel while insuring breakaway-ability, small knobs or protrusions may be placed proximate opposing edges of the door panel. These knobs or protrusions typically engage a portion of a side column guiding the door panel, increasing the resistance of the door in response to force from wind or air pressure on the door. However, these knobs or protrusions may offer less resistance than is necessary in the face of a moderate or high wind load, and under extreme forces, like for example if the door or any of its components are impacted by an object, these knobs or protrusions may break off the door panel, eliminating any wind load resistance benefit they provide. In order to replace the knobs, a person must remove the door from the side column and individually replace each knob or protrusion.
It yet further designs, segmented or spaced apart thickened portions may be attached to the door panel proximate each edge. While these wind locks are generally successful in breaking away in a zipper like fashion when the door panel is impacted by an object, they too may have problems standing up to the highest of winds.
As such, it would be advantageous to create a door assembly having a door panel having a thickened edge wind lock capable of withstanding the highest wind loads while also allowing for the door panel to controllably break away should the door panel be impacted by an object.
It would be further advantageous if the thickened edges were capable of winding in a manner that reduces the size of the roll of the door panel when in a substantially open position.
It would be still another advantage if the thickened edges were configured so as to be lighter in weight, to reduce the stress on the motor and the door panel.
The present invention is directed to solving these and other problems.